Early heart iron overload in beta thalassemia major patients can be quantified through T2* cardiovascular magnetic resonance (CMR). To clarify the value of tissue Doppler imaging (TDI) in early detection of myocardial dysfunction in iron loaded thalassemia patients diagnosed by CMR. Two groups were included in the study; Group I: 69 asymptomatic thalassemia patients (28 females, 41 males), mean age 18.1 ± 7.03 years (range 6-39 years); Group II (n = 41) healthy normal controls matched for age and sex. Serum ferritin and CMR were performed to assess the cardiac siderosis (T2* < 20 ms). Group I was subdivided into two subgroups; Group Ia (n = 26) T2* < 20 ms and Group Ib (n = 43) T2* > 20 ms. Conventional and Doppler echocardiography of LV, RV dimensions and functions and pulmonary artery pressure were evaluated. Right ventricular diastolic function assessed by tricuspid annular E'/A' was positively correlated with T2* value; lower tricuspid E'/A' ratios were correlated with lower T2* values (r = 0.366, P = 0.002). Tricuspid annular A' was significantly higher in group Ia compared to group Ib (16.7 ± 5.2 vs 12.1 ± 4.0 cm/s, P < 0.001). Tricuspid E'/A' < 1 was common in group Ia compared to group Ib (19/26 (73.0) vs 3/43 (6.97%), P < 0.001). By multivariate analysis, right ventricular diastolic dysfunction (tricuspid E'/A' < 1) was associated with serum ferritin and T2* level of the thalassemia patients. TDI is a promising tool for quantitative assessment of myocardial function and early detection of right ventricular diastolic dysfunction in iron loaded beta thalassemia major patients.